Low molecular weight unsymmetrical Ethers such as MTBE, ETBE are produced from iso-olefins and methanol/Ethanol reaction in the presence of acidic sulfonated ion exchange catalyst (e.g. Amberlyst 15 or 35 or equivalent) to produce ethers and are commonly added to the gasoline so as reduce the pollution due to better burning qualities of these Ethers and Lower vapor pressure as well, which provide good burning gasoline, due to additional oxygen added through alcohol, and the combustion products have reduced CO in the combustion products. As this addition of Ethers was mandated by the Clean Air act of 1990 by EPA. These ethers have much higher octane and lower RVP of the gasoline blend that reduces the VOC's in the atmosphere. Addition of these compounds works as diluent also, which in turn reduce the other components of the gasoline blend like benzene, aromatics and olefins. In recent years due leakage of MTBE from the gas stations storage tanks, some leaks from using it in water skies in lakes, and as solubility of the MTBE in water is high, it has created controversy as regards to suitability of the ethers in gasoline especially in USA. Some over 20 odd states in USA have banned Ether addition in gasoline, and other states might follow the trend, though it is still being used in RFG in some states in USA. In USA approximately 230,000 bbl/d of Ethers was being used in the gasoline, and if it is taken away as being suggested and is being forcasted, it will have at least about 70,000 bbl/d of shortfall of gasoline if Iso-octene is produced. Thus producing of Iso-octene via this route will be a low cost option. But if the Isobutylene can be alkylated with other normal olefins in the alkylation plant (which is normally being done for n-butenes if MTBE units are upstream) and lot of the Alkylation plants will have revamped any way. The product will be higher than the Ethers but of lower octane. But one should note that alkylate is one of the most desirable component of the gasoline pool with reasonable high octane, no aromatics and no sulfur. But the alkylation plants need much higher investment and some cases would make economic sense to produce Iso-octene and/or iso-octane via dimerization route and than if need be hydrogenating the product to reduce the olefin content, and it all depends on the economics of each plant and the specification and the complexity of the refinery which produces the gasoline components.
The invention is in the field of dimerization of isobutylene in the presence sulfonated resin catalyst (e.g. Amberlyst 15 or 35 or equivalent), together with an trifunctional catalyst which is essentially resin catalyst doped into palladium (two bed approach in the reactor) and a new selectivator for solvating the catalyst which is Isopropyl alcohol. The configuration is provided to dilute the isobutylene in the feed to 5% or less by unique configuration and recycle of Iso-propyl alcohol and dual bed catalyst provides selective conversion of Isobutylene to dimer (Iso-octene), essentially 10 to 20% of the 1-butene plus 2-butenes also goes in the reaction to form codimers. In the reaction some trimer is also formed with small amount of tetramer and also some C8 Ethers as will be shown in the reaction Chemistry section of this patent. The palladium-doped resin catalyst selectively hydrogenates the butadiene and also stabilizes the olefins, which provide the longer catalyst life, as it does not polymerize on the catalyst.
The present disclosure and the art describes a process for producing Iso-octene and Iso-octane by dimerizing the isobutylene in C4 stream in the fixed bed down flow reactor(s). In general, isobutylene dimerization process is done in the presence of similar acid catalysts that are used for etherification. We have selected a dual and different catalyst to do the dimerization to enhance the catalyst life. Essentially, the process uses an art of using a small amount of selectivator for solvating the catalyst that helps in the reactions sites to available for the reaction. The catalyst pore size and properties are selected for enhancing the catalyst activity/life. The special catalyst have been listed in the later process description and are claims of the process so as to make dual catalyst beds an art claimed by this process. together with the special selectivator/solvating agent.
The Hydrogenation is designed either to use dual catalyst system, Nickel and followed by Palladium in the finishing reactor (one can use either of the catalyst in both the reactors if so desired). Provision is there to use Palladium Platinum catalyst in the finishing Reactor as an extension of this invention.